Betatrons can be used to accelerate electrons and produce x-ray radiation for large object inspection purpose. Electrons are injected from a gun and then accelerated when circulating near a fixed-radius orbit. In inspection applications, electrons are typically accelerated to several MeV and then extracted as a pulse to hit a metal target to produce x-rays. The x-rays can be used to for cargo inspection.
However, typical betatrons provide only a single energy during an output session. To provide a different energy, a new session with different parameters or a different betatron device would need to be used. Whereas, linear accelerators that provide electron pulses of different energy from pulse to pulse have been developed in recent years. These different energies can provide additional information for inspection purposes.
A betatron typically operates at up to 300 or 400 pulses per second. But, the frequency during an output session would be a fixed value. Again, to provide a different energy, a new session with different parameters or a different betatron device would need to be used. Thus, traditional betatrons have the following disadvantages: the pulse frequency is not readily adjustable, the electron energy is not readily switchable from pulse to pulse, energy for expansion action is not recovered, and radiation output is not controllable from pulse to pulse.
Therefore, it is desirable to have methods and betatron devices that can provide adjustable pulse frequency and provide electron energy that is adjustable from pulse to pulse, as well as other advantages.